(1) Field of the Invention
The present invention relates generally to tilt tray conveyors of the type used to sort packages or parcels and, more particularly, to an apparatus for tipping the trays of such a conveyor system.
(2) Description of the Prior Art
Tilt trays conveyor systems are shown, for example, in U.S. Pat. Nos. 3,945,485 and 4,102,448, issued to Speaker, and U.S. Pat. No. 4,635,785, issued to Prydtz. The general arrangement of such systems include a track and a conveying chain on which are mounted a plurality of carriages spaced along the chain. Each carriage has a tray which is mounted for normal positioning and for tipping for one, the other or both sides of the direction of movement of the chain. Parcels or the like to be sorted are carried on the trays and transported by the conveyor to a location where sorting is to occur. At the sorting location the trays are tipped to one side or the other to discharge the transported article from the conveyor. Typically, control over the tipping is exercised by some sortation controlling means such as a computer which sequentially controls the tipping device. Prior tipping devices have been pneumatically actuated cylinder devices in which some striker element is moved upwardly into the path of an advancing carrier to engage an actuating cam on the carrier and cause tipping.
U.S. Pat. Nos. 4,982,828 and 4,856,642, issued to Nicholson, are drawn to an improved lever arm for a tilt tray sortation conveyor having a formula defined unlatching and tipping cam section. FIG. 2 in both of these patents shows a conventional tipping apparatus which includes a tipping arm and wheel mounted to a bracket attached adjacent to the conveyor track and a pneumatic actuator. However, as can be seen, a substantial amount of the force impact onto the tip-up wheel is transmitted to the pneumatic cylinder.
U.S. Pat. No. 4,174,773, issued to Venzke, discloses a tip-up and mounting apparatus in a sortation conveyor which includes a support angle, upstanding mounting angles, mounting brackets, and a tray engaging roller mounted on crank arms pivoted to the mounting brackets. The mounting angles are disposed of their apices facing outwardly of the conveyor, thus providing a mounting surface at 45 degrees to the conveyors machine direction for the mounting bracket. The crank arms are pivoted to the mounting bracket which provides an in and out component of motion to the rollers during the movement to and away from the sortation tray engagement, thereby maintaining a short roller dwell time and the tray interfering position. However, such an arrangement has a large mass located on the crank arm and roller which requires a correspondingly large pneumatic actuator. In addition, significant amounts of force may be transmitted from the crank arm through the actuator, resulting in a shortened life of the actuator assembly.
Thus, their remains a need for a new and improved tipping apparatus which is operable to reliably engage and tip the appropriate carriage on the track, while, at the same time is inherently stable and requires a much smaller pneumatic actuator for operation.